Yes, that would be my thought, too. That mom began very early to teach him this 'story' and she knew bits and pieces herself were true ... but it seems awful far-fetched. Over a 3 year period? Still ... people will do some odd things to keep themselves amused. Anything is possible.
Maybe he has had a babysitter, grandmother, aunt, or something, who has told him stories that he has assimilated as true. Young children have virtually NO ability to sort truth from fiction.
A child’s longing for a father is very intense, and could result into his latching on to this narrative as a fixation. I don’t know what has really happened here, but there are a variety of possibilities for this boy to have acquired his belief in the story without anyone’s intending to upset him.
"At the University of Virginia, a department has been set up to investigate these stories."
A Department !!! You must think the folks at UVa are either stupid or naive.
ML/NJ